The invention disclosed herein pertains to a machine for transferring graphical and decorative images from a moving web to moving articles such as containers including plastic and glass bottles and metal cans.
Machines for transferring graphics and decorative images printed in the negative or reverse form on a web with heat transferable ink are basically known. The ink images on the web, whether for decorating a container or for providing graphical information will be characterized herein selectively as "graphics". The transfer process will be characterized as "decorating" for the sake of brevity. For optimized graphics transfer of an image from the web to a container it is usually necessary to heat the container and the web before the web is pressed against the container to transfer the graphics at a transfer station. The web is coated with a release agent which assures that no trace of the ink will remain on the web after thermal transfer.
Containers that are to be decorated are conveyed linearly uniformly spaced apart and rotated about their own axes as they pass the transfer station and are transported on a turntable so the containers arrive at the transfer station in phase with graphics on the web.
Existing thermal ink graphics transfer machines have been found to be disadvantageous because they must be run at unacceptably low speeds in order to obtain reasonably accurate positioning and appearance of the decoration on the containers. These machines are not suitable for use in a production line with other apparatus that may process containers that are fed to the thermal transferring machine at rates of five or more times the rate at which the existing machines can be operated. Precise positioning of graphics on a bottle or can is especially important where a graphics label or decoration is to be applied to the front of bottles or cans and other decorations are to be applied to the backs of the bottles or cans. In such cases the decoration or labeling on the front and back of the container must be diametrically opposite of each other. For prior thermal ink transfer decorating machines to be widely acceptable it would be necessary for the machines to decorate containers at speeds of five hundred containers or more per minute. Insofar as applicant is able to ascertain, speeds of this magnitude have never been achieved before the invention to be described herein was made.
It is elementary that any thermal ink graphics transferring machine must unwind a roll of web bearing uniformly spaced apart graphics. Various satisfactory wind and unwind systems are available since they have been used for a long time in other labeling machines. The technology for maintaining proper web feed rates and tension is also known. Designers of web handling or transporting apparatus have been reasonably successful in achieving low inertia web handling systems so the web can be accelerated and decelerated rapidly to correct for positional errors between the graphics and place where the moving web and graphics ought to be relative to each other when graphics transfer occurs. If the inertia within the web handling system is high, there is an increased probability of the web being stretched or broken when it is being accelerated.
One of the reasons why the output of decorated containers from existing graphics transfer machines has been less than optimum results from designers failing, before the invention disclosed herein was made, to realize or understand what the relationship should be between the speed and direction of the web, the rotational speed and rotational direction of the container and the translational direction of the container.